1. Technical Field
The present invention relates to a sensor device, an image forming apparatus, and a control method for a light source, more specifically, relates to a sensor device suitable for identifying an object, an image forming apparatus including the sensor device, and a control method for a light source in the sensor device.
2. Description of the Related Art
In an image forming apparatus such as a digital copying machine and a laser printer, a toner image is transferred to a surface of a recording medium represented by a printing paper, and the image is fixed by performing heating and pressing under predetermined conditions, thereby forming an image. Important points to be considered in forming an image is conditions of a heating amount and pressure at the time of fixing the image, particularly in order to form a high-quality image, fixing conditions are needed to be individually set in accordance with a recording medium.
This is because image quality in the recording medium is largely affected by material quality, thickness, humidity, smoothness, coating condition, etc. of the recording medium. For example, as for smoothness, a toner fixing rate at a recessed portion in an uneven portion of a printing paper surface may be decreased by the fixing conditions. Therefore, when fixing is not performed under proper conditions suitable of the recording medium, color unevenness may occur.
Further, due to advancement of the image forming apparatus and diversification of a representation method in recent years, several hundred different types of printing papers exist only in terms of the printing paper. Moreover, a wide variety of brands exist in each type of the printing paper due to differences in specifications such as grammage and thickness. In order to achieve high-quality image forming, the fixing conditions are needed to be set in detail in accordance with each one of the brands.
Further, recently, the number of brands is also increased in terms of a regular paper, a coated paper represented by a gloss coated paper, a mat coated paper, and an art coated paper, a plastic sheet, and a special paper having a surface embossed.
In the current image forming apparatus, a user needs to set the fixing conditions by oneself at the time of printing. Therefore, the user is required to have knowledge to identify paper types, and further, the user is bothered to input setting content every time by oneself in accordance with the paper type. Also, in the case where the setting content is incorrect, an optimal image cannot be obtained.
In view of this, an optical sensor may be provided, which detects a type of paper before an image is formed on the paper.
For example, JP-2012-127937-A discloses an optical sensor including: an irradiation system that irradiates a surface of a sheet-like object with linear polarization in a first polarization direction from an incident direction tilted against a normal direction of the surface; a first optical detection system that includes a first optical detector disposed on an optical path of light regularly reflected at the object irradiated by the irradiation system; and a second optical detection system that includes an optical device and a second optical detector, the optical device being disposed on an optical path of light diffused and reflected at the object within an incidence plane of the object, and transmitting a linear polarization component in a second polarization direction orthogonal to the first polarization direction, and the second optical detector that receives the light transmissive through the optical device.
However, according to the optical sensor disclosed in JP-2012-127937-A, there may be a case where the light emitted from a light source leaks.